"In connection with the 140th anniversary of the ending of the 1877-1878 Russian-Turkish war and the liberation of Bulgaria, the head of state has invited his Russian counterpart to make an official visit to our country in 2018," the statement reads. "President Putin expressed gratitude for the invitation and accepted it, the date of the visit will be announced later," the Bulgarian presidential press service added.

"During the 20-minute conversation initiated by the Bulgarian president, deep historical and spiritual ties between the Bulgarian and Russian people were highlighted. The Russian president also thanked President Radev for his contribution to the development of bilateral relations," the statement says.

According to the Kremlin press service, the parties confirmed their willingness to boost cooperation in various spheres, including the energy sector. "Preparations for joint activities dedicated to important dates have been discussed, which include the 25th anniversary of the signing of the Treaty on Friendly Relations and Cooperation (August 4, 2017), and the 140th anniversary of the liberation of Bulgaria from the Ottoman rule (March 3, 2018)," the Kremlin press service said.

Besides, Russia and Bulgaria agreed to continue contacts on various levels, the Kremlin press service added.